This invention concerns air bag safety systems and more particularly a deployment door installation for forming an air bag deployment opening through an interior trim piece at the time of initiation of activation of the air bag system to allow the air bag to be deployed within the passenger compartment as it is inflated.
Air bags are normally stored in a folded condition in a receptacle or canister mounted behind a section of the interior trim, i.e, typically behind the instrument panel for a passenger side front seat air bag installation. A steering wheel cover is often employed as the interior trim piece behind which the air bag is stored.
The deployment opening has commonly been provided by one or more deployment door panels fit into an opening within the interior trim. The deployment doors are hinged along one side and to swing open by pressure exerted by inflation of the air bag. See U.S. Pat. No. 4,893,833 issued on Jan. 16, 1990, for a "Closure for an Air Bag Deployment Opening" and U.S. Pat. No. 4,989,896 issued on Feb. 5, 1991, for a "Double Door Closure for an Air Bag Deployment Opening" for examples of such deployment door installations.
In these designs, the deployment doors are formed of a separate panel from the interior trim piece in which the door is fit and thus is readily visible to an occupant of the vehicle.
There has been heretofore proposed various designs for a so called "invisible seam" deployment door installation in which the outline of the deployment door or door is not visibly delineated in any way to the vehicle occupant, so as to not encourage tampering also to lessen any apprehension created by the conspicuous pressure of the air bag.
See for examples, U.S. Pat. No. 5,080,393 issued on Jan. 14, 1992, for a "Method and Apparatus for Forming an Air Bag Deployment Opening"; U.S. Pat No. 5,217,244 issued on Jun. 8, 1993, for "Arrangement for Forming an Air Bag Deployment Opening"; U.S. Pat. No. 5,082,310 issued on Jan. 21, 1992, illustrates both an invisible seam and conventional deployment door design in respective embodiments shown therein.
In such invisible seam deployment door installations, the general arrangement heretofore proposed has included a trim piece substrate having an opening formed therein, with a one or more deployment door substrate panels fit within the trim piece substrate opening, each door panel hinged along one side. Both the trim and door panel substrates are overlain by a layer of molded foam such as polyurethane foam material which in turn is overlain by a decorative covering layer of a durable material such as vinyl.
The covering layer extends in a smooth uninterrupted expanse over both the portions of the adjacent trim piece substrate and one or more deployment door substrate panels such as to not suggest the presence of the deployment door lying beneath the decorative covering layer.
However, in this design, the deployment door panels, when hinged open, force the foam layer over the door substrate panel into the foam layer over the trim substrate located immediately adjacent the hinging side of the deployment door. Particularly at extremely low temperature ambient conditions, it has been discovered that the deployment door will extend itself upon hinging open, such as to strike the inside of the windshield for those deployment door designs in which the hinging access is located close to the inside of the windshield and the deployment door when opened swings towards the windshield.
Since the air bag inflates with considerable force, and the deployment doors open with a resultant high angular velocity, shattering of the windshield and scattering of glass shards into the passenger compartment is a potential hazard.
A further effect has been the disintegration of the covering layer and foam material adjacent the hinging side of the deployment door with the result in fragmentation of these materials. This is also potentially a hazard, as possibly causing showering of debris into the passenger compartment due to the high velocities with which the door swings open.
Accordingly, it is an object of the present invention to provide an improved construction for so-called hidden seam air bag deployment doors which involve a foam layer extending over both the deployment door and trim piece substrate.